Response of Dayside Auroras and Ionospheric Plasma Flows to a Solar Wind Pressure Pulse
Abstract
Global ultraviolet auroral images from the IMAGE satellite are used to investigate the response of the dayside auroral oval to a sudden impulse (SI) in the solar wind pressure. The observations are supplemented by the TV all-sky camera images over Svalbard in the pre-non sector. We show that after the SI, new discrete auroral forms appear in the poleward part of the auroral oval so that the middle of the dayside oval moves poleward from about 70 to about 73 deg. AACGM latitude. This poleward shift started in the 15 MLT sector, then similar shift was observed in the MLT sectors located more westerly, and eventually the shift was seen in the 6 MLT sector. Thus, the auroral disturbance "propagates" westward (from 15 MLT to 6 MLT) at an apparent speed of the order of 7 km/s. We show that the above auroral disturbances are associated with the westward propagating convection vortex as inferred from the global convection maps produced by the SuperDARN HF radars. The poleward boundary of the auroral oval did not show any prominent motion associated with the SI. The optical and radar observations can be interpreted in terms of the pressure disturbance propagation through the magnetosphere at a velocity of the order of 200 km/s that is essentially slower than a magnetosonic (fast Alfvén) wave, and generation of a potential (curl-free) electric field in the wake of the disturbance. We suggest that the interchange instability is a possible reason for the development of discrete dayside auroral forms after the SI. We discuss the reasons for the slow propagation speed of the disturbance and for a vortex-like convection pattern associated with the auroral motions.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSMSM42A..06K
- Keywords:
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- 2704 Auroral phenomena (2407);
- 2712 Electric fields (2411);
- 2740 Magnetospheric configuration and dynamics;
- 2784 Solar wind/magnetosphere interactions